Electrical apparatus



March .29, 1927. 1,622,531

w. s. MOODY ELECTRICAL, APPARATUS Filed Nov. 4. 1925 Inventor: Walter S. Moody,

y His Attorr'iey.

' aratus ca HGQDY, @F'PITTSFIELD, l JQHPANY A Application filed November li ily invention relates to electrical apparatus and more particularly to the encased oil immersed type of electrical apparatus such as a transformer having a winding s connected to a switch for changing the connections. is desirable that the witch be close to the apparatus so that the leads to the winding taps may be short and this end it has been customary to locate the switch inside the casing and immersed the oil withthe apparatus; A switch so located, however, is more or less inaccessible inspection or repair and it is not always convenient to locate switch inside the ap- 4 g with proper mechanical and electrical clearances without increasing the size of the casing, particularly in conneci with apparatus operating at very high gesh Then the switch is located in the body of oil with the apparatus too, it be safely "operated while carrying the switch contacts l affect the insulating qualities of the oil. "he general object of the invention is to provice an improved arrangement in which the witch is readily accessible, in which the ap leads are reasonably short and in which both the switch and the tap leads are elect ically and mechanically well protected. Another object of the invention is to provide an improved arrangement whereby the switch may be operated if desired while cari current without danger of affecting he insulating qualities of the oil in which he apparatus is immersed.

@ther objects and advantages will appear from the following description taken in connection with the accompanying drawing in which Fig. l is a view, partly in section of an encased oil immersed transformer with a tap switch arranged in accordance with e invention, and Fig. 2 is a circuit diagram of the tap switch with its connections to one of the transformer windings.

Like reference characters indicate similar parts in both figures of the drawing.

The invention is illustrated in the drawing in connection with a transformer 10 immersed in a body of insulating oil within a casing 11. This casing 11 is' completely filled with oil at all times; an expansion chamber 12 being provided to permit expansion and contraction of the oil due to changes in its temperature. A. tap changing switch is connected by tap leads i i to one the windings of the transformer so the number of effective turns in this winding may be changed as desired by changing the position of the movable contactor of the switch.

The switch 13 is enclosed in a casing '16v supported by a hollow bracket 17 secured to the side of the transformer casing 11 near the the leans c. These tap leads extend from the switch 13 tothe winding 15 through the hollow bracket 1? and through an opening in transformer casing 11 at the point where the bracket is attached so that the leads are completely protected and reasonably short. The switch casing 16 and the passageway through the bracket 17 are filled with oil for insulating purposes. An important advantage of this construction is that necessity for insulating bushings is avoided where the tap leads 14 pass through the wall of the transformer casing.

in some cases, it may be desirable to operate the switch 13 while the transformer is under load and the switch is carrying current. To permit this to be done without affecting the insulating qualities of the oil surrounding the transforimzr a barrier or seal 18 is provided in the passageway be- 'ween'the-switch casing 16 and the trans former casing 11 to prevent interchange of oil between the two casings. Arcing at the switch contacts may afiect the oil in the switch casing 16 but this oil is prevented by the seal 18 from entering the transformer casing The switch casing 16 should be oil tight to prevent leakage. it is not necessary. however, that the seal 18 be absolutely oil tight as the oil pressures on its opposite sides are equal and any simple form of SE' 'TS, ASSIGHQR T0 GEITERAL ELEC winding 15 to which it is connected by What I claim as new and desire to secure mersed, there being a passageway between said two casings, said passageway entering the side of said apparatus casing near said apparatus, tap leads extending through said passageway from said tap switch to the winding of said apparatus, said'passageway containing insulating oil surrounding said tap leads, and a seal to prevent interchange of oil between said two casings through said passageway.

2. The combination with electrical apparatus having a Winding, of a tap switch, a casing enclosing said apparatus, a separate casing enclosing said tap switch, said two casings containing insulating oil in which said apparatus and tap switch are immersed, there being a passageway between said two casings, said passageway entering theside of said apparatus casing near said apparatus, tap leads extending through said passageway from said tap switch to the winding of said apparatus, said passageway containing insulating oil surrounding said tap leads, said tap switch casing being oil tight to prevent leakage of oil, and a seal to prevent interchange of oil between said two casings through said passageway.

In witness whereof I have hereunto set my hand this 2nd day of Nov.1925.

I WALTER S. MOODY. 

